The monetary value of automobiles is extremely high as is the value of earth moving and construction equipment. Vehicles, often, have to be parked in areas where the owner can not exercise close supervision. Vehicles and equipment, frequently, must remain unguarded for several days. Professional thieves have developed techniques to steal entire vehicles, when parked in unguarded areas, by bypassing the locking devices or to exchange expensive engines or parts with wornout ones, even when parked in guarded parking areas.
Manufacturers have responded to this problem and developed devices that require special codes to gain entrance to the car or that sound alarms on unauthorized entry. Other devices require special procedures to start the engine of the vehicle or permit the engine to run. Practically all of these devices can be disabled or bypassed by a knowledgeable thief since these devices are accessible either in the cabin or in the engine compartment and are powered by the vehicle.
Any device that shall improve a car's or other motor driven equipment's resistance against the skillful manipulation of a professional thief must be designed so that neither makeshift connections on the terminals of the engine accessories nor the tampering with the security device nor the removal of power will disable the security system or permit the engine to start. One way to achieve this, is to make the protective system an internal part of the engine block or its attached vital accessories, such as the starter, the ignition system, the fuel pump or the like. In this manner it becomes impossible to access, remove, replace or disable the protective system as long as the engine block is in its place.
This places great size limitations on the security module, as it must be small enough to fit inside the vital accessory (e.g. the distributer, the solenoid of the starter, the electrical fuel pump, etc.). All security modules of a vehicle would have to be interfaced with a central control unit at the dashboard or a master control to receive the authorization codes and to signal their disabled state. Such interface is done with communication links (e.g. electrical or fiber optic), which are by nature vulnerable to tampering and allow a thief to inject false code words into the security modules. Means must be provided that prevent a hi-tech thief to enter codes in succession but must allow the rightful owner to enter the right code after he made a mistaken entry and must allow the rightful owner to enter the right code after a thief has tried to enter one or several wrong code words.